WESTFIELD — Westfield High School was under an active lockdown for what Westfield Police call “an unspecified security threat” until approximately 3 p.m.

According to Westfield Public Schools, “Earlier today, suspicious writing was discovered at Westfield High School, prompting an immediate security response and a lockdown out of an abundance of caution. Working closely with the Westfield Police Department, a thorough investigation was conducted. As this is a police matter, no additional details can be shared at this time.”

Police said that they were “actively” searching the building and sources inside say that students were checked by magnetometer wands.

Westfield Police said at 1:38 p.m. that, “The Police Department is continuing with its search efforts of each room and every individual in the building, which is a lengthy and thorough process that takes time to complete. The Union County K-9 unit is also on-scene to assist.”

This incident comes less than a week after neighboring Clark high school was sent into lockdown over what sources say was a note indicating a firearm on premises.

This is a developing story. The Leader will provide additional information as it becomes available.